1. Field of the Invention
The invention is generally related to septic tanks and, more particularly, to septic tanks of two piece construction and to a means for maintaining a septic tank firmly within the ground without the use of an anchor or ground screw.
2. Description of the Prior Art
Septic tanks are typically used at dwellings which are not connected to public water and sewer facilities. The septic tank is located underground and is basically a batch sewage processor. Sewage from the dwelling is sent to the septic tank where it is acted on by microorganisms. Through biochemical reactions, the sewage is decomposed. Subsequently, liquid and gaseous effluent is discharged into the surrounding soil. Solids remaining within the tank are periodically cleaned to prevent scum and sludge from backing up into the home.
Because the septic tank is essentially a hollow compartment for receiving fluids, there will be a tendency for it to lift up out of the more dense surrounding ground. The "buoyancy" of the septic tank is especially pronounced in tanks made from fiberglass, plastics, and resin materials, as opposed to concrete. To counteract the "buoyancy force", tanks are often anchored or held to the ground using a ground screw.
Septic tanks are typically transported by truck in unitary form. Thus, the truck is carrying mostly air, since the inside of the septic tank is hollow. U.S. Pat. No. 4,961,670 to McKenzie et al. and U.S. Pat. No. 5,242,584 to Hoarau show typical examples of unitary, molded septic tanks. It would be advantageous to design the septic tank to be transportable as two or more component parts where the component parts can be nested together during transport, and subsequently assembled together on-site prior to installation. This type of design should allow many more septic tanks to be transported by the same truck than occurs with current practice. U.S. Pat. No. 4,325,823 to Graham and U.S. Pat. No. 4,886,605 to Herve show septic tank designs where the tanks are assembled from separately manufactured top and bottom sections. However, the Graham and Herve septic tank designs do not allow on-site assembly of the septic tank. Hence, the Graham and Herve designs do not allow for the transport of additional septic tanks on a truck.
U.S. Pat. No. 3,426,903 to Olecko discloses a multi-component septic tank and specifically shows the entire assembly in a nesting or packaged configuration in FIG. 2. The nesting configuration of Olecko essentially allows a single septic tank to occupy half the space it would otherwise occupy if it were fully assembled. It would be advantageous to have a nesting scheme which allowed for more dense packing of septic tanks for transportation purposes than is allowed by the Olecko design.